1. Field of the Invention
This invention relates to a spotlight assembly mounted on the roof of an automotive vehicle, and more particularly to means for ventilating the interior of the lamp unit of the spotlight assembly.
2. Prior Art
U.S. Pat. No. 5,217,291 dated Jun. 8, 1993 is directed to a hand operated spotlight assembly mounted on the roof of an automotive vehicle and having a lamp unit mounted for movement between an inoperable retracted position and an erect operable position. A handle inside the vehicle adjacent the roof is gripped manually for pivoting and rotating the lamp unit to a desired position of the light beam from the lamp unit. The lamp unit is mounted for unlimited rotational movement and for tilting pivotal movement in a generally vertical plane. The lamp unit in a retracted inoperable position faces in an upward direction to direct a light beam in a generally vertical direction.
Automotive auxiliary light systems fall into two categories, one category being sealed-beam lamps and the other category being those which are not sealed. The primary difference between the two is that sealed beam lamps are manufactured and sold as a complete assembly including lens, reflector, and light generating lamp element sealed with a vacuum or specific gases. Sealed beam lamps are discarded and replaced in their entirety if any component therein fails. Non-sealed beam lamps incorporate light generating elements in compact glass envelopes that contain the necessary gases essential to high levels of light output and extended operating life. The lens and reflective walls of the lamp are separate parts of the assembly. The typical point of failure in any lamp is the light generating element or bulb. Non-sealed beam lamps allow the user to access and replace the light element or bulb independently without having to discard and replace the reflector, lens, etc. An additional advantage of non-sealed beam lamps is that lamp designers are allowed much more freedom of design for specific applications.
Due to the extreme variance in ambient temperatures surrounding the lamp to the heat levels achieved within the lamp during extended periods of operation, non-sealed beam lamps must be vented so that pressure inside the lamp can be equalized with outside pressure. While a very small opening is adequate to equalize this pressure, moisture vapor is inevitably drawn into the lamp vent with the air taken into the lamp as the lamp cools after operation. This moisture condenses on internal parts of the lamp once such pans have cooled. This moisture can be detrimental to the performance of the lamp assembly over a period of time.
It is the object of this invention to provide a non-sealed beam lamp unit that uses air flow produced by vehicle motion to ventilate the interior of the lamp unit and to actively remove moisture from the interior of the lamp unit.